The present invention relates to game rackets in general, and in particular to a tennis racket having means for reducing the shock, vibration, and muscular strain received by the player, when used by the player in a game.
Prior art rackets having conventional weight and stiffness distribution have considerable shock and vibration transmitted to the player's hand, when the ball impacts the racket at locations other than the center of percussion.
U.S. No. 4,165,071 issued to Frolow Aug. 21, 1979, provided a prior art racket having an unconventional stiffness and weight distribution which provided for a reduction in the shock and vibration received by the player's hand upon impact of the racket with the ball. The racket disclosed by Frolow was easy to move because of its reduced weight, the torque or moment at the player's hand when the racket was held by the player's hand as a cantilever was reduced, the center of percussion was located closer to the point on the racket string netting which was more frequently impacted by the ball in play. This racket had the same hitting power as conventional prior art rackets by maintaining the required moment of inertia or swing weight.
However, when the ball did impact the racket at locations other than the center of percussion, the player's hand absorbed the shock and vibration which did occur.
The present invention utilizes the unconventional weight and stiffness distribution of the racket disclosed by Frolow and also provides a system comprising a weight means and a means for the attachment of the weight means to the handle portion of the racket, for reducing further the shock and vibration received by the player's hand during the impact of the racket with the ball and the vibration subsequent to the impact.
U.S. Pat. No. 3,941,380 issued to Lacoste Mar. 2, 1976, provided a weight means attached to the handle end of a racket. The weight and restoring resiliency was designed to vibrate in correspondence to the vibration induced in the racket, when the ball impacted the racket.The weight means absorbed the energy at this single frequency of vibration. The weight means disclosed must be designed differently for each racket having a different structure.
The patent to Lacoste disclosed a racket having a conventional weight distribution and it was vey flexible and had considerable vibration at a low frequency induced in it upon impact with a ball. This racket had the weight of conventional prior art rackets, and the additional weight means added by Lacoste results in a heavy racket.
The present invention provides a weight means fastened to the handle portion of the racket and the movement between the weight means and the handle portion does not vibrate at the frequency corresponding to the frequency of vibration of the movement between the racket frame and the hand of the player, induced in the racket when the racket impacts the ball. In column 4, lines 22 to 26 Lacoste indicates that if the frequency of the amortizing system is less than 45 Herz one finds the difference between the frequency of the amortizing system itself and the frequency of the frame is too great to permit the amoritization to be significant. Since the frequency of the frame f.sub.1 was 100 Herz, this difference between the frequencies is 55 Herz, and thus a frequency of the amortizing system itself outside the range of f.sub.1 .+-.0.55 f.sub.1, will not permit the damping to be significant. This range cooresponds to frequencies less than 0.45 f.sub.1 and greater than 1.55 f.sub.1. The present invention provides a weight means which absorbs the energy of the shock and vibration at all the frequencies of vibration that occur.
Also the present invention provides for a racket having a light weight, a center of percussion close to the center of the racket face, a low torque at the player's hand, when the racket is held as a cantilever by the player, the same hitting power as prior art rackets, and a reduction over the prior art in the shock and vibration transmitted to the player's hand upon the racket impacting the ball.
U.S. Pat. No. 4,364,564 issued to Lewis Dec. 21, 1982, discloses a device which is worn on a player's wrist to absorb the shock experienced by a player in a game of tennis or the like. This device does not interact directly with the racket which generates the shock and vibration to the player's hand upon impact of the ball.
The present invention absorbs the energy before it gets to the player's hand and also reduces the shock and vibration generated by the racket upon impact with the ball.
U.S. Pat. No. 4,153,249 issued to Plangenhoef May 8, 1979, discloses a slight mechanical modification to a conventional prior art racket to make the racket more compatible with the mechanics of the human arm, more comfortable to use and reduce the strain on the arm of the player. This patent discloses a conventional prior art racket with a weight attached to the handle end and a side weight attached to one side of the head portion of the racket. The patent discloses that the magnitude of the weights are adjusted to coact and provide for the center of percussion taken about a center of rotation which is located at 43/4 inches from the handle end, to be located between 22/27 and 23/27 of the racket length from the handle end of the racket, and the center of gravity to be located at a distance slightly less than half the length of the racket.
The use of the side weight on one side of the racket head increases the weight of the racket given by W, increases the distance of the center of gravity to the handle end given by Cg, and increases the moment of inertia of the racket about the handle end. These increases result in the torque or moment at the handle end held in the hand of the player as a cantilever given by the product WCg to be very high, as well as make the racket difficult to swing and maneuver. Conventional prior art rackets and the racket disclosed by Plagenhoef have a high torque at the end of the racket handle held in the hand of the player and the addition of this side weight makes this torque more unfavorable. The racket disclosed by plagenhoef has a weight W of 430 to 440 grams or 15.136 oz to 15.488 oz and the distance of the center of gravity Cg to be from 12 to 13 inches, thereby resulting in a torque given by WCg to be 182 to 197 oz-inches at the player's hand. These values are exceptionally high.
The increase in weight to the conventionl prior art rackets, makes the racket difficult to maneuver. The racket disclosed by Plagenhoef has a weight of 15.136 oz to 15.488 oz which is very high.
The present invention provides for a racket having a torque given by the product WCg, and a weight W which is much less than the racket disclosed by Plagenhoef, and further provides for means which effectively reduces the shock and vibration to the hand and body of the player.
U.S. Pat. No. 3,999,756 issued to Head Dec. 28, 1976, discloses a racket having a strung area having a length along the longitudinal axis of the racket to be between 12 and 15 inches, and the width of the strung area to be between 91/2 and 111/2 inches in a direction perpendicular to the longitudinal axis of the racket.
The center of percussion of a racket similar to that of the racket disclosed, the Prince GRAPHITE, taken about the handle end measured to be 18.1 inches from the handle end.
The present invention provides for a racket having a strung area having a width being greater than 12 inches, which is as large as the racket disclosed by Head, but provides for a center of percussion which is greater than 18.1 inches, and provides for a weight much less than 12 ounces, thereby making the racket much easier to maneuver, and providing for much less shock and vibration being transmitted to the player, when the racket impacts the ball.